Telephone signaling system



`-June 28, 1932. W H EDWARDS 1,864,645

TELEPHONE SIGNALING SYSTEM Filed June 27, 1931 INVENTOR ATTORNEY Patented June 28, 1932 UNITED y, STATES PATENT .OFFICE WILLIAM H. EDWARDS, 0E GREAT NECK, NEW YORK',V AssIGfNoR To AMERI'GAN TELE- PHONE AND TELEGRAPH'COMPANY, AcoRPoRA'rIoN von NEW YORK TELEPHONE SIGNAINGF SYSTEM Application led June 27,

This invention relates to telephone systems and more particularly to improvements in signaling arrangements associated with such systems.

One of the primary objects of the invention consists in providing at a telephone station a visual signal, such for example as a neon lamp7 operated by the ringing voltage applied to the line. A further obj ect of the invention consists in providing improved means for associating the visual signal with the line so that adequate voltage for operating the lamp may be obtained without the use of transformers for stepping up `the applied ringing voltage and without the use of relays .and separate sources of voltage. Further objects of the invention consist in providing means for so associating the visual signal with the line that false operation thereof may be avoided from dialing impulses and from certain typesV of testing currents. Other objects and features of the' invention will appear more fully from the detailed'description thereof hereinafter given.

In the arrangements of the inventionfthe O visual signal, or neon lamp, is connected d1- rectly across the condenser of the usual ringing apparatus connected across' the line at the station. The arrangements of the invention thus make use of the resonant eect of the station ringer circuits to obtain from the applied ringing current thehigh voltage necessary to break down the neon lamp inasmuch as the peak ringing voltage across the condenser is higher than across the ringer and condenser. As impulses set up bythe dial-y ingA operation, which might'fcause false operation, are relatively high ,in frequency there is relatively little voltage drop Iacross the ringing condenser as it is of relatvelylow impedance to the frequencies having the highest voltage. of the inventionrprevent the visual signal from being operated falsely on the impulses set up by dialing. In the arrangements of the Accordingly, the arrangements 1931. I Serialr N0'. 5475335.

invention a condenser may also be provided trated. Fig. 1 is a circuit diagram illustrating a preferred embodiment of the invention. Figs. 2 and 3 are vector diagrams illustrating the principles of operation of the invention.`

In Fig. 1 is shown a telephone line L terminating in a subscribers station. Bridged across the line would be theusual station ringing apparatus comprising the rcondenser 1 and ringerl 12.V The subscribers apparatus comprises the usual induction coil, the condenser 7, switchhook contacts 8 and 95 the transmitter 10Y and the receiver 11. Bridged directly across'the ringing condenser 1 is a circuit 3 including thejcondenser `at andthe visual signal device 5, whichmay be a neon lamp. A neon lamp hasthe characteristic that it requires a certain minimum peak voltage to cause it to break down, which is substantially lindependent of frequency; In order to obtain the relatively .high voltage toV cause the tube to break down which in certain commercial neon lamps is approximately 110 volts it is connected directlyacross the ringingr condenser 1 as shown. The tube will break down and operate when alternating Aringing current is applied to the line under those conditions. By connecting the neon lamp to the linein the manner shown the arrangementsof the invention make use of the resonant effect ofthe station ringer circuit to obtain froml the applied ringing ycurrent the high voltage necessary lto break down the neon lamp inasmuch as the peak ringing voltage across the condenser is higher than `across the.

ringerv and condenser. y This will appear V--voltage across line at station=50vvolts R. M. S.

L=inductance of ringer at 1015f-f=39.5

henries. Y

R=effective Aresistance'of ringer at 191/6-NV =3000 ohms. C capacity of condenser 1.0 microfarads.

The total impedance Z across the line-is determined as follows:

contacts at relatively slow speed is such that oscillations of relatively high frequency and voltage are produced across the line at the station. Assuming a frequency of 200 cycles for these oscillations, which is of course only representative inasmuch as there is a wide range of frequencies in the oscillations produced under different station conditions, the following values are obtained.

Vd=voltage across line due to dialing=350 Volts effective.

Ld=inductance of ringer at 200 =8.35 henries.

Rd=effective resistance of ringer at 200 8000 ohms.

C capacity ofk condenser= 1.0 microfarads.

Obtainingrthe total impedance across the line in a manner similar to that described Z :4650 ohms.

V# 50 I- Z-4-65-0 .01075 amperes.

y Referring to Fig. 2, which is a vectordiagram showing thevoltage drops across the various portions of the circuit, it will be seen fronivector A that if the neon lamp is connected across the line 'it will Vreceive a voltage of 50 volts R. M. S. which ordinarily is insuticient to break it down inasmuch asapproximately 78 volts effective or 110 Volts peak 1s required for this purpose. It will appear from vector B that if the neon lamp were connected across the ringer it would obtain 60.4 volts effective due to the combined drop across the resistance and inductive reactance of the ringer. It will appear from vector C, however, thatV if'the neon lamp were -connected across the condenser in accordance with the arrangements of the invention that the condensive reactance drop amounts to 89.3 volts effective. This is sufficient to break down and operate the neon lamp as the maximum instantaneous voltage is approximately 126 volts. K I g Y It has been pointed out that the arrangementsv of the invention will prevent false operation from dialing impulses. This will be more readily understood from the vector diagram of Fig. 3, in discussing which certain values for circuit conditions will beassumed for purposes of illustration. Under dialing conditions the make and break of the dial heretofore, it appears that Zd= 12,600 ohms Referring to the vector' diagram of Fig. 3 showing the voltage drop across various portions of the circuit under dialing conditions, it will be seen from vector D that if the neon lamp is connected across the line the voltage of 350 volts would be sufficient to break it down and operate it falsely. Likewise it will appear from vector E that if the neon lamp were connected across the ringer the combined resistance and reactance drops would amount to 369 volts, which would operate the lamp falsely. However, if the lamp is connected across the 1.0 mf. condenser in accordance with the arrangements of the invention it will appear from vector F that the condensive reactance drop amounts to onlyV 22.3 volts effective Yor 31.5 volts maximum instantaneous which is insufficient to operate the lamp. Accordingly, the arrangements of the invention will prevent the signal lamp from operating falsely on impulses due to dialing.

The condenser 4; of Fig. 1 in series with the lamp will serve to prevent continued false operation of the lamp on the usual insulation and breakdowntest made from the test desk.

A further use of the Signaling arrangements of the invention might arise in con- Y nection With 10W-voltage code calling or auX- iliary signaling systems in which 48 volt, 60 cycle alternating current is sent over telephone Wiring to operate 60 cycle telephone ringers. A maximum value of approximately 48 volts is desirable from a protection standpoint, but is insuiiicient to operate coinmercial neon lamps directly. However, by connecting the neon lamp in the resonant ringer circuit across the terminals of the condenser or the ringer, Whichever has the highest voltage, the neon lamp can be operated satisfactorily.

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and other Widely varied forms Without departing from the spirit of the invention as dei-ined by the appended claim. What is claimed is:

A telephone line terminating at a subscribers station, ringing apparatus comprising a condenser and a ringer bridged across said line at said station, and a signaling cir- 80 cuit connected directly across said condenser, said signaling circuit including a condenser and a cold cathode discharge tube.

[n testimony whereof, I have signed my name to this specification this 26th day of June, 1931.

WILLIAM H. EDWARDS 

